Watchtower

Watchtowers are automated turrets on an indestructible tower of Tyvian Steel that targets enemies with explosive firebolts.

Watchtowers are powered by Whale Oil, but whether or not the fuel cell is depleted when the device fires is unknown. Watchtowers can be hacked with a rewire tool to ally with Corvo (and target your enemies).

Although it is difficult to get onto the platform of one of these turrets to rewire it, they are extremely deadly. Climb on the rooftops to Blink onto the platform, then rewire the device and it will quickly eliminate every enemy in sight.

Be extremely careful around Watchtowers, as they will see you easily. They rotate around with a large spotlight and will not only do lots of damage to you, but will also reveal your location to guards. It is best to take care of Watchtowers before you progress, so that they don't pose a threat later in the level.